<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python documentation Index' />
<link rel="first" href="lib.html" title='Python library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="incremental-encoder-objects.html" />
<link rel="prev" href="codec-base-classes.html" />
<link rel="parent" href="codec-base-classes.html" />
<link rel="next" href="incremental-encoder-objects.html" />
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<meta name='aesop' content='information' />
<title>4.8.1.1 Codec Objects </title>
</head>
<body>
<div class="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.8.1 codec Base Classes"
  href="codec-base-classes.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="4.8.1 codec Base Classes"
  href="codec-base-classes.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="4.8.1.2 incrementalencoder Objects"
  href="incremental-encoder-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="codec-base-classes.html">4.8.1 Codec Base Classes</a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="codec-base-classes.html">4.8.1 Codec Base Classes</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="incremental-encoder-objects.html">4.8.1.2 IncrementalEncoder Objects</a>
</div>
<hr /></div>
</div>
<!--End of Navigation Panel-->

<h3><a name="SECTION006811000000000000000"></a><a name="codec-objects"></a>
<br>
4.8.1.1 Codec Objects 
</h3>

<p>
The <tt class="class">Codec</tt> class defines these methods which also define the
function interfaces of the stateless encoder and decoder:

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-537' xml:id='l2h-537' class="method">encode</tt></b>(</nobr></td>
  <td><var>input</var><big>[</big><var>, errors</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
  Encodes the object <var>input</var> and returns a tuple (output object,
  length consumed).  While codecs are not restricted to use with Unicode, in
  a Unicode context, encoding converts a Unicode object to a plain string
  using a particular character set encoding (e.g., <code>cp1252</code> or
  <code>iso-8859-1</code>).

<p>
<var>errors</var> defines the error handling to apply. It defaults to
  <code>'strict'</code> handling.

<p>
The method may not store state in the <tt class="class">Codec</tt> instance. Use
  <tt class="class">StreamCodec</tt> for codecs which have to keep state in order to
  make encoding/decoding efficient.

<p>
The encoder must be able to handle zero length input and return an
  empty object of the output object type in this situation.
</dl>

<p>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-538' xml:id='l2h-538' class="method">decode</tt></b>(</nobr></td>
  <td><var>input</var><big>[</big><var>, errors</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
  Decodes the object <var>input</var> and returns a tuple (output object,
  length consumed).  In a Unicode context, decoding converts a plain string
  encoded using a particular character set encoding to a Unicode object.

<p>
<var>input</var> must be an object which provides the <code>bf_getreadbuf</code>
  buffer slot.  Python strings, buffer objects and memory mapped files
  are examples of objects providing this slot.

<p>
<var>errors</var> defines the error handling to apply. It defaults to
  <code>'strict'</code> handling.

<p>
The method may not store state in the <tt class="class">Codec</tt> instance. Use
  <tt class="class">StreamCodec</tt> for codecs which have to keep state in order to
  make encoding/decoding efficient.

<p>
The decoder must be able to handle zero length input and return an
  empty object of the output object type in this situation.
</dl>

<p>
The <tt class="class">IncrementalEncoder</tt> and <tt class="class">IncrementalDecoder</tt> classes provide
the basic interface for incremental encoding and decoding. Encoding/decoding the
input isn't done with one call to the stateless encoder/decoder function,
but with multiple calls to the <tt class="method">encode</tt>/<tt class="method">decode</tt> method of the
incremental encoder/decoder. The incremental encoder/decoder keeps track of
the encoding/decoding process during method calls.

<p>
The joined output of calls to the <tt class="method">encode</tt>/<tt class="method">decode</tt> method is the
same as if all the single inputs were joined into one, and this input was
encoded/decoded with the stateless encoder/decoder.

<p>

<div class="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="4.8.1 codec Base Classes"
  href="codec-base-classes.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></a></td>
<td class='online-navigation'><a rel="parent" title="4.8.1 codec Base Classes"
  href="codec-base-classes.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up one Level' width='32' /></a></td>
<td class='online-navigation'><a rel="next" title="4.8.1.2 incrementalencoder Objects"
  href="incremental-encoder-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></a></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></a></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></a></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="codec-base-classes.html">4.8.1 Codec Base Classes</a>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="codec-base-classes.html">4.8.1 Codec Base Classes</a>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="incremental-encoder-objects.html">4.8.1.2 IncrementalEncoder Objects</a>
</div>
</div>
<hr />
<span class="release-info">Release 2.5.1, documentation updated on 18th April, 2007.</span>
</div>
<!--End of Navigation Panel-->
<address>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</address>
</body>
</html>
